My boyfrirnd has a rash in groin area and under armpit he also has been on antibiotics for mrsa and pnemonia caused by a spider bite that had necrosis?

A lot to consider. MRSA is a type of bacteria, not a diagnosis. Does he have a MRSA pneumonia? How is that related to a brown recluse spider? Which antibiotics delivered how, at what doses, for how long? He must have been very ill. Sounds like he has monilial intertrigo related in part to antibiotics. If this is the case, he will improve with miconazole cream, Castellani's solution, and a single dose of oral flucona.